They make their money on the hardware that they sell and the ASICs in there are fairly specific to them. Opening up their software stack is hardly a big step, most companies don't do it because their products can easily be cloned by nefarious manufacturers (this is quite common in China). If you have such a secure position that no one can copy your hardware (e.g Juniper & Cisco won't), then you can do this with impunity.
If this software actually helped commoditise the high end product then I would be happy, but I doubt it will.